Field of the Invention
The use of ultrasonic transducers as distance sensors is known in robotics technology, both for recognizing an object and for positioning a movable element, such as an arm, of the robot. The low propagation velocity of the ultrasonic pulses, in comparison with electro magnetic radiation, permits a simple and direct measurment of the distance between the robot arm, or its gripper or tool, and the target object to be grasped or processed. The local resolution and precision of the guidance of such a robot arm on the basis of signal evaluation of ultrasonic echo signals is very high, and increases with decreasing distance, that is, as the robot arm approaches the target object. Moreover, ultrasonic transducers are small and light weight and can thus be mounted in a simple fashion on a robot arm.
An ultrasonic transducer which is particularly well suited for this application is described in German Pat. No. 2,541,492. This transducer has very good directional characteristics with comparatively small dimensions. Transducers of this type can be mounted on a robot arm in large numbers without impairing the other functions of the arm, such as the attachment of grippers or tools thereto.
Distance measurement with ultrasound is undertaken by transmitting a transmit pulse, receiving the reflected pulse from a target object, and evaluating the time delay of the received pulse with respect to the time of transmission of the transmit pulse. In making the evaluation, however, a distinction must be made between echo signals which originate from objects other than the target object. There are many methods known in the art for distinguishing such echo signals from each other.